We are interested in how bacteria and bacterial products shape the development of subsequent innate and adaptive immune responses with the goal of understanding how these host-microbe interactions influence pathogenesis of infections, autoimmunity, allergy, and cancer. In particular, we have focused on the role of interleukin (IL)-17 and related cytokines in mucosal host defense. In 2012, we have investigated host immune responses against pathogens at the skin (Staphylococcus aureus), lung (Cryptococcus), and gut (Citrobacter). These studies have resulted in insights into the regulation of IL-17-related cytokines and their role in protection against these infections. With these studies we have enhanced our understanding of the mechanisms controlling mucosal T cell differentiation and identified potential pathways that can be targeted to enhance efficacy of vaccines and therapies against cancer, infectious, and immune-mediated diseases.